In olefin polymerizations in which late transition metal complexes of selected ligands, such as xcex1-diimines, are used as polymerization catalysts, various compounds, such as hydrogen or selected silanes, may be used as chain transfer agents to reduce polyolefin molecular weight.
Polymerization of olefins using early transition metal containing catalysts such as vanadium and zirconium is a well known and commercially important technology. In many instances it is desirable to lower the molecular weight of the polyolefin that would normally be produced. For example lower molecular weight polymers are usually considered easier to melt process, since they have lower melt viscosities. While polymerization process conditions can sometimes be altered to change the molecular weight of the resulting olefin, often a chain transfer agent such as hydrogen is deliberately added to the process to lower the polyolefin molecular weight.
The polymerization of olefins using late transition metal containing catalysts such as nickel with selected bidentate ligands is known, see for instance U.S. Pat. No. 5,714,556, World Patent Application 96/23010, and U.S. patent application Ser. No. 09/006,536, filed Jan. 13, 1998, now U.S. Pat. No. 6,174,975 (World Patent Application 98/30609). However, methods for lowering the molecular weight of polyolefins produced in such processes are not well known. Since these processes often give polyolefins with unique and valuable structures, methods for controlling the polymer molecular weight are desirable.
This invention concerns, a process for the polymerization of a polymerizable olefin using as a polymerization catalyst a complex of a bidentate ligand of a metal selected from the group consisting of nickel, iron, and cobalt, wherein the improvement comprises, using as a chain transfer agent an effective amount of hydrogen, CBr4 or a compound of the formula R1R2R3SiH, wherein R1 is alkyl containing 2 or more carbon atoms, R2 is alkyl, and R is hydrogen or alkyl.
This invention also concerns a process for the polymerization of one or more polymerizable olefins, comprising, contacting:
(a) one or more polymerizable olefins;
(b) an effective amount of a chain transfer agent selected from the group consisting of hydrogen, CBr4 and a compound of the formula R1R2R3SiH, wherein R1 is alkyl, R2 is alkyl, and R3 is hydrogen or alkyl;
(c) an active polymerization catalyst which contains a nickel complex of a ligand of the formula 
or a compound of the formula 
xe2x80x83wherein:
Ar1 is an aromatic moiety with n free valencies, or diphenylmethyl;
each Q is xe2x80x94NR52R53 or xe2x80x94CR54xe2x95x90NR55;
p is 1 or 2;
E is 2-thienyl or 2-furyl;
each R52 is independently hydrogen, benzyl, substituted benzyl, phenyl or substituted phenyl;
each R54 is independently hydrogen or hydrocarbyl; and
each R55 is independently a monovalent aromatic moiety;
m is 1, 2 or 3;
R53 is hydrogen or alkyl;
each R16 and R17 is independently hydrogen or acyl containing 1 to 20 carbon atoms;
each R33, R34, R35, and R36 is independently hydrogen, hydrocarbyl or substituted hydrocarbyl;
each R31 is independently hydrocarbyl or substituted hydrocarbyl containing 2 or more carbon atoms;
each R32 is independently hydrogen, hydrocarbyl or substituted hydrocarbyl;
Ar2 is an aryl moiety;
R38, R39, and R40 are each independently hydrogen, hydrocarbyl, substituted hydrocarbyl or an inert functional group;
R37 and R41 are each independently hydrocarbyl, substituted hydrocarbyl or an inert functional group whose Es is about xe2x88x920.4 or less;
Ar3 is an aryl moiety;
R45 and R46 are each independently hydrogen or hydrocarbyl;
Ar4 is an aryl moiety;
Ar5 and Ar6 are each independently hydrocarbyl;
Ar7 and Ar8 are each independently an aryl moiety;
Ar9 and Ar10 are each independently an aryl moiety or xe2x80x94CO2R56, wherein R56 is alkyl containing 1 to 20 carbon atoms;
Ar11 is an aryl moiety;
R50 is hydrogen or hydrocarbyl;
R51 is hydrocarbyl or xe2x80x94C(O)xe2x80x94NR50xe2x80x94Ar11;
R44 is aryl;
R47 and R48 are each independently phenyl groups substituted by one or more alkoxy groups, each alkoxy group containing 1 to 20 carbon atoms;
R49 is alkyl containing 1 to 20 carbon atoms, or an aryl moiety;
R13 and R16 are each independently hydrocarbyl or substituted hydrocarbyl, provided that the carbon atom bound to the imino nitrogen atom has at least two carbon atoms bound to it;
R14 and R15 are each independently hydrogen, hydrocarbyl, substituted hydrocarbyl, or R14 and R15 taken together are hydrocarbylene substituted hydrocarbylene to form a carbocyclic ring;
R18 is hydrocarbyl or substituted hydrocarbyl, and R20 is hydrogen, hydrocarbyl or substituted hydrocarbyl or R18 and R20 taken together form a ring;
R19 is hydrocarbyl or substituted hydrocarbyl, and R21 is hydrogen, substituted hydrocarbyl or hydrocarbyl, or R19 and R21 taken together form a ring;
each R17 is independently hydrogen, substituted hydrocarbyl or hydrocarbyl, or two of R17 taken together form a ring;
R27 and R30 are independently hydrocarbyl or substituted hydrocarbyl;
R28 and R29 are each in independently hydrogen, hydrocarbyl or substituted hydrocarbyl; and
n is 2 or 3;
Ar12, Ar13, Ar15, Ar16, Ar22, Ar23, Ar24, and Ar25 are each independently aryl or substituted aryl;
R56 and R57 are each independently hydrogen, hydrocarbyl, substituted hydrocarbyl, or R57 and R57 taken together form a ring, and R58 is hydrogen, hydrocarbyl or substituted hydrocarbyl or R56, R57 and R58 taken together form a ring;
each R31 is independently hydrogen, substituted hydrocarbyl or hydrocarbyl, or two of R31 taken together form a ring;
R22 and R23 are each independently hydrocarbyl or substituted hydrocarbyl, provided that the carbon atom bound to the imino nitrogen atom has at least two carbon atoms bound to it;
R24 and R25 are each independently hydrogen, hydrocarbyl, or substituted hydrocarbyl;
A is a xcfx80-allyl or xcfx80-benzyl group;
R63 and R67 are each independently hydrogen, hydrocarbyl or substituted hydrocarbyl;
R62, R61, R60, R59, R66, R65, R64, R70, R69, R68, R76, R77, R78, R79, R80, R81, R88, R89, R90, R91 and R92 are each independently hydrogen, hydrocarbyl, substituted hydrocarbyl, an inert functional group, and provided that any two of these groups vicinal to one another taken together may form a ring;
R73 is hydrocarbyl, substituted hydrocarbyl, xe2x80x94SR132, xe2x80x94OR132, or xe2x80x94NR1332, R72 is hydrogen, a functional group, hydrocarbyl or substituted hydrocarbyl, and R71 is hydrocarbyl or substituted hydrocarbyl, and provided that R73 and R72 or R72 and R131 taken together may form a ring;
R82, R83, R84 and R85 are each independently hydrogen, hydrocarbyl, substituted hydrocarbyl, or an inert functional group;
R86 and R87 are each independently hydrogen, hydrocarbyl or substituted hydrocarbyl;
w is 1, 2 or 3;
Ar26, Ar17, Ar18, Ar19, Ar20 and Ar21 are each independently hydrocarbyl or substituted hydrocarbyl;
R132 is hydrocarbyl or substituted hydrocarbyl;
each R133 is independently hydrogen, hydrocarbyl or substituted hydrocarbyl;
G and L are both N or G is CR134 and L is CR135;
R135, R93 and R134 are each independently hydrogen, hydrocarbyl or substituted hydrocarbyl, or any two of R93, R134 and R135 taken together form a ring;
R94, R95, R96, R97, R98, R99, R100, R101, R102, R103 and R104 are each independently hydrogen, hydrocarbyl, substituted hydrocarbyl, or a functional group;
R105, R106, R107 and R108 are each independently hydrocarbyl or substituted hydrocarbyl;
R109 and R110 are each independently hydrocarbyl or substituted hydrocarbyl;
R111, R112, R113, and R114 are each independently hydrogen, hydrocarbyl, substituted hydrocarbyl or a functional group;
both of T are S (sulfur) or NH (amino);
each J is N (nitrogen) or CR136 wherein R136 is hydrogen, hydrocarbyl, substituted hydrocarbyl or a functional group;
R115, R116, R117, R118, R119, R120, R121, and R122 are each independently hydrogen, hydrocarbyl, substituted hydrocarbyl, or a functional group;
R123, R124, R125, R126, R127, R128, R129, and R130 are each independently hydrogen, hydrocarbyl, substituted hydrocarbyl or a functional group; and
R74 and R75 are each independently hydrogen, hydrocarbyl or substituted hydrocarbyl;
and provided that when said ligand is any one of (XXV) through (XXXVI) said transition metal is nickel.
In the polymerization processes and catalyst compositions described herein certain groups may be present. By hydrocarbyl is meant a univalent radical containing only carbon and hydrogen. By saturated hydrocarbyl is meant a univalent radical which contains only carbon and hydrogen, and contains no carbon-carbon double bonds, triple bonds and aromatic groups. By substituted hydrocarbyl herein is meant a hydrocarbyl group which contains one or more (types of) substituents that does not interfere with the operation of the polymerization catalyst system. Suitable substituents in some polymerizations may include some or all of halo, ester, keto (oxo), amino, imino, carboxyl, phosphite, phosphonite, phosphine, phosphinite, thioether, amide, nitrile, and ether. Preferred substituents are halo, ester, amino, imino, carboxyl, phosphite, phosphonite, phosphine, phosphinite, thioether, and amide. Which substituents are useful in which polymerizations may in some cases be determined by reference to World Patent Applications 96/23010 and 97/02298, and U.S. Pat. No. 5,714,556. By (substituted) hydrocarbylene is meant a group analogous to hydrocarbyl, except the radical is divalent. By benzyl is meant the C6H5CH2xe2x80x94 radical, and substituted benzyl is a radical in which one or more of the hydrogen atoms is replaced by a substituent group (which may include hydrocarbyl). By an aryl moiety is meant a univalent group whose free valence is to a carbon atom of an aromatic ring. The aryl moiety may contain one or more aromatic ring and may be substituted by inert groups. By phenyl is meant the C6H5xe2x80x94 radical, and a phenyl moiety or substituted phenyl is a radical in which one or more of the hydrogen atoms is replaced by a substitutent group (which may include hydrocarbyl). Preferred substituents for substituted benzyl and phenyl include those listed above for substituted hydrocarbyl, plus hydrocarbyl. If not otherwise stated, hydrocarbyl, substituted hydrocarbyl and all other groups containing carbon atoms, such as alkyl, preferably contain 1 to 20 carbon atoms.
By a styrene herein is meant a compound of the formula 
wherein R140, R141, R142, R143 and R144 are each independently hydrogen, hydrocarbyl, substituted hydrocarbyl or a functional group, all of which are inert in the polymerization process. It is preferred that all of R140, R141, R142, R143 and R144 are hydrogen. Styrene (itself) is a preferred styrene.
By a norbornene is meant ethylidene norbornene, dicyclopentadiene, or a compound of the formula 
wherein R145 is hydrogen or hydrocarbyl containing 1 to 20 carbon atoms. It is preferred that R145 is hydrogen or alkyl, more preferably hydrogen or n-alkyl, and especially preferably hydrogen. The norbornene may be substituted by one or more hydrocarbyl, substituted hydrocarbyl or functional groups in the R145 or other positions, with the exception of the vinylic hydrogens, which remain. Norbornene (itself), dimethyl endo-norbornene-2,3-dicarboxylate, t-butyl 5-norbornene-2-carobxylate are preferred norbornenes and norbornene (itself) is especially preferred.
By a xcfx80-allyl group is meant a monoanionic ligand with 3 adjacent sp2 carbon atoms bound to a metal center in an xcex73 fashion. The three sp2 carbon atoms may be substituted with other hydrocarbyl groups or functional groups. Typical xcfx80-allyl groups include 
wherein R is hydrocarbyl. By a xcfx80-benzyl group is meant xcfx80-allyl ligand in which two of the sp2 carbon atoms are part of an aromatic ring. Typical xcfx80-benzyl groups include 
xcfx80-Benzyl compounds usually initiate polymerization of the olefins fairly readily even at room temperature, but xcfx80-allyl compounds may not necessarily do so. Initiation of xcfx80-allyl compounds can be improved by using one or more of the following methods:
Using a higher temperature such as about 80xc2x0 C.
Decreasing the bulk of the monoanionic ligand, such as aryl being 2,6-dimethylphenyl instead of 2,6-diisopropylphenyl.
Making the xcfx80-allyl ligand more bulky, such as using 
rather than the simple xcfx80-allyl group itself.
Having a Lewis acid or a material that acts as a Lewis acid present while using a xcfx80-allyl or xcfx80-benzyl group, especially a functional xcfx80-allyl or xcfx80-benzyl group. Relatively weak Lewis acids such as triphenylborane, tris(pentafluorophenyl)borane, tris(3,5-trifluoromethylphenyl)borane, and poly(methylaluminoxane) are preferred. Suitable functional groups include chloro and ester.
Where applicable, Es refers to the steric effect of a group. The steric effect of various groupings has been quantified by a parameter called Es, see R. W. Taft, Jr., J. Am. Chem. Soc., vol. 74, p. 3120-3128 (1952), and M. S. Newman, Steric Effects in Organic Chemistry, John Wiley and Sons, New York, 1956, p. 598-603. For the purposes herein, the Es values are those described in these publications. If the value for Es for any particular group is not known, it can be determined by methods described in these publications. For the purposes herein, the value of hydrogen is defined to be the same as for methyl. It is preferred that the total Es value for the ortho (or other substituents closely adjacent to the xe2x80x94OH group) substitutents in the ring be about xe2x88x921.5 or less, more preferably about xe2x88x923.0 or less. Thus in a compound such as 2,4,6-tri-t-butylphenol only the Es values for the 2 and 6 substituted t-butyl groups would be applicable.
Noncoordinating ions are mentioned and useful herein. Such anions are well known to the artisan, see for instance W. Beck., et al., Chem. Rev., vol. 88, p. 1405-1421 (1988), and S. H. Strauss, Chem. Rev., vol. 93, p. 927-942 (1993), both of which are hereby included by reference. Relative coordinating abilities of such noncoordinating anions are described in these references, Beck at p. 1411, and Strauss at p. 932, Table III. Useful noncoordinating anions include SbF6xe2x88x92, BAF, PF6xe2x88x92, or BF4xe2x88x92, wherein BAF is tetrakis[3,5-bis(trifluoromethyl)phenyl]borate.
A neutral Lewis acid or a cationic Lewis or Bronsted acid whose counterion is a weakly coordinating anion may also be present as part of the catalyst system. By a xe2x80x9cneutral Lewis acidxe2x80x9d is meant a compound which is a Lewis acid capable of abstracting an anion from a late transition metal compound to form a weakly coordination anion. The neutral Lewis acid is originally uncharged (i.e., not ionic). Suitable neutral Lewis acids include SbF5, Ar3B (wherein Ar is aryl), and BF3. By a cationic Lewis acid is meant a cation with a positive charge such as Ag+, H+, and Na+.
In many of those instances in which the transition metal compound does not contain an alkyl or hydride group already bonded to the metal, the neutral Lewis acid or a cationic Lewis or Bronsted acid also alkylates or adds a hydride to the metal, i.e., causes an alkyl group or hydride to become bonded to the metal atom, or a separate (from W) compound is added to add the alkyl or hydride group.
A preferred neutral Lewis acid, which can alkylate the metal, is a selected alkyl aluminum compound, such as R93Al, R92AlCl, R9AlCl2, and xe2x80x9cR9AlOxe2x80x9d (alkylaluminoxanes), wherein R9 is alkyl containing 1 to 25 carbon atoms, preferably 1 to 4 carbon atoms. Suitable alkyl aluminum compounds include methylaluminoxane (which is an oligomer with the general formula [MeAlO]n), (C2H5)2AlCl, C2H5AlCl2, and [(CH3)2CHCH2]3Al. Metal hydrides such as NaBH4 may be used to bond hydride groups to the metal M.
For (IV) through (XXIV) preferred formulas and compounds (as ligands for polymerization catalysts) are found in World Patent Applications 96/23010 and 97/02298, both of which are hereby included by reference, and preferred grouping and compounds in these applications are also preferred herein. However the compound numbers and group (i.e., Rx) numbers in these Applications may vary from those herein, but they are readily convertible. These applications also describe synthesis of the various ligands. A preferred ligand is (IV).
There are many different ways of preparing active polymerization catalysts of transition metal coordination compounds of compounds as described herein, many of which are described in World Patent Applications 96/23010 and 97/02298, and those so described are applicable herein. xe2x80x9cPurexe2x80x9d compounds which themselves may be active polymerization catalysts may be used, or the active polymerization catalyst may be prepared in situ by a variety of methods.
For instance, olefins may be polymerized by contacting, at a temperature of about xe2x88x92100xc2x0 C. to about +200xc2x0 C. a first compound W, which is a neutral Lewis acid capable of abstracting an anion to form a weakly coordinating anion; or a cationic Lewis or Bronsted acid whose counterion is a weakly coordinating anion; a second compound such as 
and one or more polymerizable olefins wherein:
M is an appropriate transition metal;
R146 and R149 are each independently hydrocarbyl or substituted hydrocarbyl, provided that the carbon atom bound to the imino nitrogen atom has at least two carbon atoms bound to it;
R147 and R148 are each independently hydrogen, hydrocarbyl, substituted hydrocarbyl, or R14 and R15 taken together are hydrocarbylene or substituted hydrocarbylene to form a ring;
Q is alkyl, hydride, chloride, iodide, or bromide; and
S is alkyl, hydride, chloride, iodide, or bromide.
In this instance it is preferred that W is an alkyl aluminum compound. Other methods for preparing active polymerization catalyst will be found in these patent applications and in the Examples herein.
Polymerizations with nickel complexes of (XXV) through (XXXVI) and compounds (XXXVII) and (XXXVIII) are described in U.S. patent application Ser. No. 09/006,536, filed Jan. 13, 1998, now U.S. Pat. No. 6,174,975 (World Patent Application 98/30609), which is hereby included by reference. It will be noted that (XXV) through (XXXVI) are monoanionic ligands. Synthesis of these ligands, their nickel complexes, and active olefin polymerization catalysts are found in this patent application, along with information on polymerization conditions. A preferred ligand (and its nickel compounds) is (XXVI). All preferred forms of these ligands and compounds are as described in U.S. patent application Ser. No. 09/006,536, filed Jan. 13, 1998, now U.S. Pat. No. 6,174,975 (World Patent Application 98/30609).
Which active polymerization catalysts will polymerize which olefins (not all catalysts will polymerize all olefins or combinations of olefins) will also be found in World Patent Applications 96/23010 and 97/02298 and U.S. patent application Ser. No. 09/006,536, filed Jan. 13, 1998, now U.S. Pat. No. 6,174,975 (World Patent Application 98/30609). Monomers useful herein include ethylene, propylene, other xcex1-olefins of the formula R150CHxe2x95x90CH2, wherein R150 is n-alkyl containing 2 to about 20 carbon atoms, cyclopentene, a styrene, and a norbornene. Preferred monomers are ethylene, propylene and cyclopentene, and ethylene is especially preferred.
For all polymerization catalysts, where applicable, nickel is a preferred transition metal.
When hydrogen is used as the chain transfer agent it is preferred that the amount of hydrogen present be about 0.01 to about 50 mole percent of the olefin present, preferably about 1 to about 20 mole percent. When liquid monomers (olefins) are present, one may need to experiment briefly to find the relative amounts of liquid monomers and hydrogen (as a gas). When a silane of the formula R1R2R3SiH is used, it is preferred that the molar ratio of transition metal compound:silane is about 0.01 to about 100,000, more preferably about 1 to about 10,000. When CBr4 is the chain transfer agent it is preferred that the molar ratio of transition metal compound:CBr4 is about 0.01 to about 1000, preferably about 1 to about 100.
When the polymerization is carried out the in the gas phase (the monomer is transported to the polymerization site while in the gas phase) hydrogen or a relatively volatile silane is a preferred chain transfer agent. The polymerization may also be carried out in solution or slurry using these chain transfer agents. In these instances, silanes are the preferred chain transfer agents.
The transition metal compounds and/or any needed cocatalysts such as alkylaluminum compounds may be supported (attached to and/or on the surface of) solid supports such as alumina, silica, and inorganic salts such as magnesium chloride. Such supported catalysts are especially useful in gas phase polymerizations. Such supported catalysts are known in the art.
In some preferred silanes, R3 is alkyl and/or both R2 and R3 have 2 or more carbon atoms and/or R1, R2 and R3 are alkyl groups independently containing 2 to 6 carbon atoms. Especially preferred silanes are triethylsilane, trimethylsilane, diethylsilane and dimethylsilane, and triethylsilane and trimethylsilane as more preferred. In another preferred silane, R1 contains 2 or more carbon atoms.
The polymers produced in these processes are useful as elastomers, molding resins, extrusion resins as for packaging films, and various other uses, depending on the properties of the resulting polymer.
In the Examples and Comparative Examples, all pressures are gauge pressures. The following abbreviations are used:
DSC-Differential Scanning Calorimetry
GPC-Gel Permeation Chromatography
MMAO-modified methyl alumoxane
Mn-number average molecular weight
Mw-weight average molecular weight
Mz-xe2x80x9czxe2x80x9d average molecular weight
PE-polyethylene
TCB-trichlorobenzene
Tm-melting point